Infinite body, rectangular coordinate transient 1-D.

G_X00(x, t | x, $\displaystyle \tau$ ) = [4 $\displaystyle \pi$ $\displaystyle \alpha$ (t - $\displaystyle \tau$ )]^-1/2exp $\displaystyle \left[\vphantom{ -\frac{(x-x^{\prime })^{2}}{4\alpha (t-\tau )}}\right.$ - $\displaystyle {\frac{(x-x^{\prime })^{2}}{4\alpha (t-\tau )}}$ $\displaystyle \left.\vphantom{ -\frac{(x-x^{\prime })^{2}}{4\alpha (t-\tau )}}\right]$